In an electron gun for cathode-ray tubes, a few components are of elongate shape in the direction of the beam or beams generated by one or more cathodes. The objective of these elongate shapes is to form said beams or to make them converge towards the screen of the tube. The first electrode of the gun, also referred to as the control electrode, may also be of elongate shape and surround the cathode or cathodes more or less totally. In this case, the elongate shape allows confinement of the energy dissipated by the cathode filaments, so as to render the latter emissive and thereby increase the energy yield of the assembly.
The control electrode G1, drilled with one or more orifices for the passage of the electron beams, may be made by deep-drawing, in such a way as to make the electrode surface and its lateral skirt from one planar component. Such an electrode G1, is for example illustrated by the Dutch patent application 8103395. It is also possible to make the electrode G1 by welding, onto the plane part drilled with orifices, a lateral skirt obtained by bending. These methods have shown their limitations since the subsequent adjusting of the cathode modules can only be done readily if the shape and final dimensions of the electrode G1 are perfectly controlled and in accordance with those specified. The methods of the prior art do not enable the shape of the electrode G1 to be controlled with sufficient accuracy.